Steering gear of four-wheel tractor

ABSTRACT

A steering gear wherein the steering shaft is alternately connected via a hydraulic servo unit and a shift coupling with a steering linkage and with a gear speed reducer installed on a shaft articulated to the front axle of the tractor. The drive shaft is installed in the housing coaxially with a shaft connected with the front axle. The drive shaft carries a gear rigidly connected with the pitman arm while the other shaft carries a planetary speed reducer with an external gear. The shift coupling consists of two coaxial sleeves provided with gear rims at the end and interconnected for joint axial movement. The inner sleeve is installed on the drive shaft and meshes alternately with said gears while the outer sleeve is connected to the housing with a freedom of axial movement and meshes with said gears for alternate locking of the front axle and steering linkage.

United States Patent 1 Tsai et al.

STEERING GEAR OF FOUR-WHEEL TRACTOR Inventors: Grigory Tsai, Kirda,Saime ulitsa Filed:

Jan. 13, 1972 Appl. No.: 217,520

Foreign Application Priority Data Jan. 29, 1971 U.S.S.R. ..1613167 US.Cl ..180/79.2 R, 280/91, 280/96 Int. Cl. ..B62d 5/06 Field of Search..l80/79.2 R, 79.4;

[56] References Cited UNITED STATES PATENTS 2,105,473 1/1938 Dean..180/79.2 R X 3,315,759 4/1967 Bohlen ..280/91 X FOREIGN PATENTS ORAPPLICATIONS 446,718 5/1936 Great Britain ..280/87 R Primary ExaminerLeoFriaglia Assistant Examiner-Leslie J. Paperner Att0rney-Holman & Stern[57] ABSTRACT A steering gear wherein the steering shaft is alternatelyconnected via a hydraulic servo unit and a shift coupling with asteering linkage and with a gear speed reducer installed on a shaftarticulated to the front axle of the tractor.

The drive shaft is installed in the housing coaxially with a shaftconnected with the front axle. The drive shaft carries a gear rigidlyconnected with the pitman arm while the other shaft carries a planetaryspeed reducer with an external gear. The shift coupling consists of twocoaxial sleeves provided with gear rims at the end and interconnectedfor joint axial movement. The inner sleeve is installed on the driveshaft and meshes alternately with said gears while the outer sleeve isconnected to the housing with a freedom of axial movement and mesheswith said gears for alternate locking of the front axle and steeringlinkage.

1 Claim, 3 Drawing Figures STEERING GEAR F FOUR-WHEEL TRACTOR Thepresent invention relates to the tractor-building industry and morespecifically it relates to the steering gear of four-wheel tractorswhose front axle is capable of turning so as to align the tracks of thesteerable wheels on turns with the track of the outer driving wheel.

Known in the art is the steering gear of a four-wheel tractor whereinthe steering shaft is divided in the plane perpendicular to itslongitudinal axis. One end of this shaft is mounted with a steeringwheel while the other end is fitted with a worm gear drive whose driveshaft carries the pitman arm of the steering linkage.

Installed before the worm gear drive on the steering shaft is a gearspeed reducer connected via bevel gear drives and a hydraulic servo unitwith the shaft which is articulated to the tractor front axle forturning the latter. The hydraulic servo unit consists of a hydraulicselector and hydraulic cylinders.

At the jointing point of the steering shaft there is a shift couplingintended for alternate connection of the steering shaft with thesteering linkage and with the front axle for turning it while changingthe direction of tractor movement.

The shift coupling consists of a movable member and a fixed member. Thefixed coupling member is rigidly secured on the steering shaft at theside of the worm gear drive. The movable coupling member is providedwith a gear rim and is installed on the steering shaft at the steeringwheel side with a provision for axial movement.

When the coupling members are engaged, the steering linkage is connectedfor turning the steerable wheels; when they are disengaged, the gear rimof the movable coupling member comes in mesh with a spur gear whose hubcarries a rigidly secured driving bevel pinion which is in constant meshwith a driven bevel gear connected with the hydraulic selector via acrankshaft.

The coupling members are engaged and disengaged by a rod one end ofwhich is connected to the movable coupling member while the other end isarticulated to a control lever in the drivers cab.

The above-described design of the steering gear for turning the frontaxle and pitman arm of the tractor fails to ensure dependable steeringsince it has no provision for reliable locking of the steering linkageand front axle when they are alternately set in operation.

An object of the present invention is to provide for reliable alternatelocking of the steering linkage and front axle of the tractor so as tolock the steering linkage on turns and to look its front axle duringstraightahead motion.

In accordance with this and other objects we hereby claim a steeringgear of a four-wheel tractor wherein the steering shaft carrying asteering wheel on one end has a hydraulic servo unit at the other end,said servo unit incorporating a drive shaft set at an angle to thesteering shaft; said steering shaft can be connected by a shift couplingeither with the pitman arm or with a gear speed reducer connected to ashaft which is articulated to the front axle of the tractor for turningit when the direction of tractor movement is changed and wherein,according to the invention, the drive shaft of the hydraulic servo unitand the shaft articulated to the front axle are coaxially installed inthe housing, one after the other; the drive shaft carries a gear capableof rotating around said shaft and rigidly connected with the pitman armwhile the other shaft carries a planetary gear speed reducer with anexternal gear, the shift coupling consisting of two coaxial sleeves withgear rims at the ends, said sleeves being connected to each other forjoint synchronous axial movement; the inner sleeve is installed on thedrive shaft with a provision for axial movement and can be meshedalternately with the gear connected to the pitman arm or with the speedreducer gear for turning the front axle of the tractor while the outersleeve is connected with said housing movable in the axial directionand, being alternately engaged with the speed reducer gear or with thegear connected to the pitman arm locks and gears against turning.

The steering gear of a four-wheel tractor realized according to thepresent invention is comparatively simple in manufacture and operationand ensures reliable locking of the steering linkage and front axle ofthe tractor both during engagement and operation.

Now the invention will be described in detail by way of example withreference to the accompanying drawings, in which:

FIG. 1 is a kinematic diagram of the steering linkage of a four-wheeltractor according to the invention;

FIG. 2 is a section taken along line IIII in FIG. 1;

FIG. 3 is a turning diagram of a four-wheel. tractor.

The steering gear of a four-wheel tractor comprises a steering shaft 1(FIG. 1) one end of which carries a steering wheel 2 and the other endis mounted with a hydraulic servo unit 3 whose drive shaft 4 is set atan angle to the steering shaft 1. Installed coaxially with the driveshaft 4 is a shaft 5 articulated to the front axle 6 on which steerablewheels 7 are mounted. These shafts are arranges so that the end of thedrive shaft 4 rests on the shaft 5 with the aid of a thrust bearing 8.The joint of this type allows the shaft 5 to stay immovable duringrotation of the drive shaft 4.

The shafts 4 and 5 are located in a housing 9 secured on the hydraulicservo unit 3. The housing can also be mounted on the tractor frame (notshown in the drawings).

Mounted on the drive shaft 4 with the aid of bearings 10 is a gear 11rigidly fastened to the pitman arm 12 of the steering linkage 13.

The shaft 5 carries a planetary speed reducer 14 comprising a sun gear15 (FIGS. 1, 2) whose hub 16 carries an external gear 17.

The sun gear 15 is connected with a gear 20 mounted on the shaft 5 viaplanet pinions 18 whose rotation axle 19 is secured on the housing 9.

The drive shaft 4 is provided with a shift coupling 24 which consists oftwo coaxial sleeves 22 and 23.

The ends of these sleeves have gear rims 24, 25 and 26, 27 withidentical pitch circle diameters. These gear rims are designed foralternate meshing with the gears 11 and 17, respectively, of the pitmanarm 12 and of the speed reducer 14 for their turning and locking.

The inner sleeve 22 is installed on the drive shaft 4 with the aid ofsplines 28 which allows it to move axi ally along the shaft 4 and rotatetogether with it.

The outer sleeve 23 is installed in the housing 9 by means of a splinedjoint 29 which permits its axial movement only.

The sleeve 22 has an annular shoulder 30 entering a slot 31 of the outersleeve 23. Such a jointing of the inner and outer sleeves 22 and 23provides for their joint synchronous movement in the axial direction.

The coupling 21 can be moved from one extreme position to the other bymeans of a rod 32 and a lever 33, the latter being installed in thedrivers cab.

The steering gear of a four-wheel tractor functions as follows.

The position of the lever 33 shown in FIG. 1 corresponds to turning ofthe tractor. The coupling 21 is in the downmost position. Meanwhile, thegear 24 of the sleeve 23 meshes with the gear 11 of the pitman arm 12while the gear 26 of the inner sleeve 22 is in engagement with the gear17.

Rotating the steering wheel 2 turns the steering shaft 1 and transmitsrotation to the drive shaft via the hydraulic servo unit 3.

The inner sleeve 22, the gear 17 meshing with it and, as a consequence,the sun gear rotate together with the drive shaft 4. Rotation of the sungear 15 is transmitted via the planet pinions 18 to the gear which isrigidly secured on the shaft 5 so that the shaft 5 connected with thefront axle turns horizontally in the direction contrary to the rotationof the steering shaft 1 through an angle B (FIG. 3). The turning angle[3 of the front axle 6 is limited by a stop (not shown) secured to thetractor frame (not shown).

The turning angle [3 of the front axle 6 with L 1.1 B where L tractorwheel base and B track width is determined on the assumption that theradius p of turning of the outer driving wheel 34 is equal to theturning radiuses p and p of the steerable wheels 7. p=p =p If theseconditions are satisfied, the angle B is determined by the formula Barctan(p,,/2 where: p distance from the center 0 of tractor turning tothe middle of the tractor driving axle 35. If this condition issatisfied, the path of the tractor front wheels 7 on turning the tractorwill coincide with the path of its outer driving wheel 34.

Turning of the front axle 6 is a vertical direction is ensured by itsarticulated jointing with the shaft 5.

Meanwhile, the gear 11 of the pitman arm 12 meshes with the gear 24 ofthe outer sleeve 23 so that the steering linkage 13 is locked againstturning while the tractor changes its direction of travelling.

Inorder to shift the tractor back to straight-ahead motion, the steeringwheel 2 is rotated in the opposite direction so as to return the frontaxle 6 to the initial position. Then the coupling 21 is brought to theuppermost position by the lever 33. The gear 25 of the sleeve 22 engagesthe gear 11 of the pitman arm 12 while the gear 27 of the outer sleeve23 engages the gear 17. Thus, the planetary speed reducer is locked inposition and the front axle 6 of the tractor occupies its initialposition.

Turning the steering wheel 2 rotates the steering shaft 1 and thisrotation is transmitted via the hydraulic servo unit 3 to the driveshaft 4. Rotating together with the shaft 4, the inner sleeve 22 drivesthe gear 11 and, consequently, moves the pitman arm 12 and the steeringlinkage 13 connected with the steerable wheels 7 of the tractor.

What is claimed is:

l. A steering gear ofa four-wheel tractor with a turning front axlecomprising: a steering shaft; a steering wheel mounted on one end ofsaid steering shaft; a hydraulic servo unit located on the other end ofsaid steering shaft; a drive shaft of said hydraulic servo unit set anangle to said steering shaft; a gear mounted on said drive shaft; apitman arm rigidly connected with said gear; a steering linkageconnected to said pitman arm and to the steerable wheels of saidtractor; a shaft articulated to said front axle and installed coaxiallywith said drive shaft; a planetary speed reducer mounted on said shaftwhich is articulated to the front axle for turning the latter; anexternal gear mounted on said speed reducer; a housing secured on astationary element of said tractor and accommodating said shafts; ashift coupling intended for alternate connection of said steering shaftwith said steering linkage and said speed reducer; said shift couplingconsists of an inner sleeve mounted on the drive shaft with a freedom ofaxial movement, gear rims secured on the ends of said inner sleeve andmeshing alternately with said gear connected with said pitman arm forturning said steering linkage and with said gear of said speed reducerfor turning said front axle of the tractor, an outer sleeve installed onsaid housing with a freedom of axial movement and connected with saidinner sleeve for joint synchronous axial movement, gear rims secured onthe ends of said outer sleeves and meshing alternately with said gear ofsaid speed reducer for locking the front axle against turning and withsaid gear connected to said pitman arm for locking the steering linkageagainst turning.

1. A steerinG gear of a four-wheel tractor with a turning front axlecomprising: a steering shaft; a steering wheel mounted on one end ofsaid steering shaft; a hydraulic servo unit located on the other end ofsaid steering shaft; a drive shaft of said hydraulic servo unit set anangle to said steering shaft; a gear mounted on said drive shaft; apitman arm rigidly connected with said gear; a steering linkageconnected to said pitman arm and to the steerable wheels of saidtractor; a shaft articulated to said front axle and installed coaxiallywith said drive shaft; a planetary speed reducer mounted on said shaftwhich is articulated to the front axle for turning the latter; anexternal gear mounted on said speed reducer; a housing secured on astationary element of said tractor and accommodating said shafts; ashift coupling intended for alternate connection of said steering shaftwith said steering linkage and said speed reducer; said shift couplingconsists of an inner sleeve mounted on the drive shaft with a freedom ofaxial movement, gear rims secured on the ends of said inner sleeve andmeshing alternately with said gear connected with said pitman arm forturning said steering linkage and with said gear of said speed reducerfor turning said front axle of the tractor, an outer sleeve installed onsaid housing with a freedom of axial movement and connected with saidinner sleeve for joint synchronous axial movement, gear rims secured onthe ends of said outer sleeves and meshing alternately with said gear ofsaid speed reducer for locking the front axle against turning and withsaid gear connected to said pitman arm for locking the steering linkageagainst turning.